Banner Photo Credit: Vancouver Fraser Port Authority
BC’s coast stretches more than 27,200 km and is home to roughly 80 percent of the province’s 4.6 million inhabitants. The shore zone region consists of the nearshore area extending from the subtidal through the intertidal zone and includes the backshore lands immediately adjacent to the shore (Fig. 1). The characteristics of these three zones (subtidal: below low tide, intertidal: between low and high tide, and backshore: all land above high tide that is within the shore zone) are directly influenced by physical, chemical, biological, and human processes. These include: wind, wave, current, and tidal energies; water pH, temperature, and salinity; flooding and freshwater influxes; sediment transport, erosion and siltation; species abundance, distribution, and life cycles; fisheries, habitat, and wildlife management; coastal development; and other human uses.
Shore zone habitat types include salt marshes, mudflats, eelgrass meadows, estuarine regions, sandy and rocky beaches, rocky reefs, glass sponge reefs, and a range of riparian habitats. Coastal development can lead to varying degrees of habitat loss and water quality degradation, and, if not done properly, can destroy economically and ecologically valuable shore zone habitat. This occurs directly through land conversion, such as infilling of the intertidal or subtidal zones, and indirectly through habitat alterations, such as water quality degradation, and increased sedimentation or erosion. Exacerbating these effects, climate change often acts synergistically with coastal development to increase the intensity of shore zone dynamics. Coastal development that does not account for projected sea-level rise, ocean pH decline, increased ocean temperature, and increased flooding and storm intensity will put critical coastal and shore zone habitats, such as estuaries, intertidal zones, and mudflats, at risk. One of the manifestations of the combined effects of climate change and coastal development is coastal squeeze: intertidal and shallow subtidal habitats diminish in area or disappear when sea level rise, erosion, and flooding induce landward migration of coastal habitats, but hard barriers, such as seawalls or dikes, prevent this migration.
To protect marine habitat integrity, shore zone project developers are encouraged to reduce on-site habitat alteration through selecting suitable sites to complement ambient natural physical and biological processes, incorporate appropriate project design practices, use environmentally sound construction methods, implement project mitigation to reduce impacts, and, as a last resort, compensate for destruction of fish habitat. Types of compensation projects that are suitable for BC marine waters and fisheries species include estuarine and salt marsh development, kelp bed construction, forage fish spawning beaches, shallow water refuges, eelgrass transplants, and rocky reef construction. This chapter provides an overview of the physical, biological, and human processes at work in British Columbia’s shore zone; summarizes a working framework for shore zone project delivery; and highlights key considerations for design, construction and monitoring for restoration projects that involve eelgrass transplant and rocky reef construction.